Electrical protective device



Aug. 28, 1923.

R. J. WENSLEY ELECTRICAL PROTECTIVE DEVICE Filed April 4, 1918 INVENTOR floqJh elraley WITNESSES Z lf/Harm A TToRNEY .EPatented Aug. 28,

302' J. WENSLEY, or nenwoon PARK, PENNSYLVANEA, ASSIGNQR TO"WE'STI1\TG- {House nrinornrc & MANUFACTURING vAjNrA. I

COMPANY, A CORPORATION or PENNSYLL I 'iinnc'r IIQA rno'rnc'rrvn- DEVICE.

Application med April 4;

Tofjll whom it may con-06m:

' [Be it knownth'at I, Bord. VVnNsLnY, af "citizen of the United States, and a resident of Edgevvood Park, in the county of Allegheny and State of Pennsylvariimhave in- "vente'd a new and useful Improvement in Electrical Protective Dev1ces,'o \vh1ch the f following .is fa specificat1on.

' ."'esp'onsive relays for use in connection with induction motors.

"-dncti'on motor. n I

Another object'of my invention 1s to pro- "of the primary winding above a predeter- V mined yalue and will vary. in accordance with the frequency of the current traversing "the primary Winding. If the primary Wind- I drawing is a di'agrammatic view of an electrical system embodying my invention.

reri't 1 traversing 'tively simple and inexpensive to construct and efiective in its operatlonfi invention relates to electrical protec-' tive' devicesan'd particularly :to frequency ,Q-;:. t fm i vention k130 provide t I a relay that shall be responsiye to the slip andf'consequently, the frequency otthe ourthe rotor inding of an 1nvide a frequency-responsive relay of the above-indicated character that shall be rela- In practicing my invention, Iifprovid'e a magnetizable core member having a leakondary'windings thereof. The core member H is of such characteristics that itis normally magnetically saturated. By this .construction, the voltage induced in the secondary Winding will be independent ofthe voltage ing is co'nnectedto the rotor Winding of an induction motor,'a relay that is connected to the secondary Winding may becaused to be responsive to'the slip'and, consequently, the load on the motor.

The single figure of the accompanying An electric circuit 1 is operativelycorinected to the primary or stator winding of an induction motor 2 that isadapted to "drive a generator 3:1;01 the purpose of sup plying energy to an electric circuitj l. ,A second motor-gene]:ator set, comprising an induction motor 5] and a generator, 6, is adapted to be connected between the circuits land 4 for the' purpose of assisting" the motor 2 and the 'g'eneratOrBfWhen the same become loaded to a predetermined degree.

Since the speed and, -consequently, the slip er the rotor of the motor 2 varies in ac- .thereon. I impressed on the winding 11. will vary in ac .cordance with thee frequency only and consequently, the slip or load on the motor 2. lVhentheload on the motor 2 has a prede- V termined value, sufiicient voltage will be 1918. Serial ITo. 256,619; r

cord'ance vvith 'th'e load on the same, and, since thefrequency of the current traversing the rotor inding of the motor 2 varies in device 7 that is responsive to thefrequency and, consequently, the slip or load onthe motor 2lor controlling the operation of the interrupter fflfor' the circuitot the motor 5.

primary inding 10 is connected i'n circuit with the rotor Winding of the motor 2 and ts controlllngresistors 12, and the secondary accordance'with' the load, I provide a relay Winding 11 is connected to the winding 13 voltage-responsive relayl l. The relay 14 1s adaptedto control a circult 15 that comprises a source 16 ofelectromotive force,

the actuating Winding 17 of the circuit interrupter 5 and contact members 181thatv arenormally in their closed positions When i the controlling resistor12 of the motor-2 is 7 short circuited. age path 'betweenthe primary and the sec- The .magnetizable core member 8 of the relay device 7 is of suchconstrnction that it is adapted to become magnetically saturated for relatively small values of current traversing the winding 10 and the A rotor windingof the.m'otor2,: and, sincethe core member 8 is provided; with aleakage path 9,

only a predetermined voltage will be induced in the .vvinding. 11, irrespective ofthecurrent traversing the windinglO above a predetermined value; However, When the speed of the motor 2 changes, by reason or" the increased load thereon, the frequency out, the current traversing the rotor inding and the Winding 10 Will be proportional to the speed of the motor 2 and, consequently the load Thus, the change in theoltage induced in thevvinding 11 to causetherel'ay 14L to operate and when therelay lt operates,

My invention is, not limited tothe specific application illustrated, as it may be applied thexcircuit 15 Will be completed to close thef core member being of such characteristics that it becomes so magnetically saturated at relatively low values of current that the potential induced in the secondary winding is proportional to the slip of the rotor;

2. In an electrical system, the combination with an induction motor'having a wound rotor, of a magnetizable core member, a primary winding for the core mem- V berconnected to the rotor winding of the motor, a secondary winding for the core member, and an electro-responsive device connected to the secondary windmg, said core member being of such characteristics that it becomes so magnetically saturated at relatively low values of current that the potential induced in the secondary winding is proportional to the frequency of the current traversing the rotor.

3. In an electrical system, the combination with an induction motor having a wound rotor, of a magnetizable core member, a primary winding therefor connected to the rotor winding and a secondary winding for the core member, said core member being of such characteristics that it becomes so magnetically saturated, at relatively low values of current traversing its primary winding, that the electromotive force in duced in the secondary winding is proportional to the frequency generated by the rotor winding, and means responsive to the induced electromotive force.

at. In an electrical system, the combination with an induction motor having a wound rotor, of a magnetizable core memher, a primary winding therefor connected to the rotor winding and a secondary wind ing for the core member, said core member being of such characteristics that it becomes so magnetically saturated, at relatively low values of current traversing its primary winding, that the electromotive force induced in the secondary winding is proportional to the slip of the rotor, and means responsive to the induced electromotive force.

5. The combination with an induction motor having a wound rotor, of a normally saturated core member, a primary winding therefor connected to the rotor winding,

and a secondary winding adapted to have the primary winding electromotive forces induced therein in accordance with the slip of the rotor, and

Vmeans responsive to the induced electromotive forces.

6. The combination with an induction motor having a wound rotor, of a magnetizable core member, a primary winding therefor connected to the rotor winding, and a secondary winding, said core member being of such characteristic that it is normally saturated to thereby cause the electromotive forces induced in the secondary winding to be proportional only to the slip of the rotor, and means responsive to the induced electromotive forces.

7. The combination with an induction motor having a wound rotor, of a relay, and a normally saturated transformer disposed between the rotor winding and the relay,

the characteristics of the transformer being such that the relay is actuated only in ac cordance with the slip of the rotor.

8. The combination with an induction motor having a wound rotor, of a relay, and a transformer disposed between the rotor winding and the relay and having such flux-controlling characteristics that the relay is actuated only in accordance with the slip of the rotor.

9. The combination with an induction motor having a wound rotor, of an electroresponsive device, and a transformer connected between the rotor winding and the said device and having such voltage transforming characteristics that the said device is supplied with current onlyin accordance with the slip of the rotor.

10. The combination with an induction motor having a wound rotor, of a normally saturated core member, a primary winding therefor connected to the rotor winding, a secondary winding adapted to have voltages induced therein in accordance with the slip of the rotor, and means responsive to that voltage.

11. The combination with a wound-rotor induction motor, of means for producing an electromotive force varying with the slip of the motor comprising a normally saturated magnetizable core member, a primary winding therefor energized from the rotor winding and a secondary winding energized by motive force varying with the motor.

12. The combination with an electric apparatus provided with a Winding movable relative to a moving magnetic flux, of means for indicating the relative movement therebetween by generating an electromotive force varying with such relative movement which comprises a primarywinding energized from the movable winding, a secondary winding energized from the primary winding, a normally saturable core member slip of the to produce an electro-' between the primary and, the secondary voltage impressed-upon the primary Wind winding for controlling the electromotive ing.

force induced in the secondary winding to In testimony whereof, I have hereunto 1 render such force responsive to the fresubscribed my name this 25th day of March 5 quency of reversal of flux in said core mem- 1918..

ber by the current traversing the primary winding and independent of changes in the 1 ROY J. WENSLEY. 

